kauth: Don't ignore GetExtendedCellInfo failures

Don't ignore a failure from afsconf_GetExtendedCellInfo, as it will
leave buffers that we later read uninitialised.

Caught by clang-analyzer

Reviewed-on: http://gerrit.openafs.org/9180
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 5cefa0247fe4f22f769e366a207fb177ee8fb94f)

Change-Id: I613a371f1f0ab1a739966e81965661d6cbff8e5e
Reviewed-on: http://gerrit.openafs.org/9531
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>